A red blood cell (RBC) count measures that amount of red blood cells in a sample and makes an overall estimate of the average count in a person's blood. These numbers are expressed in either million per microliter (uL) or million per millimeter cubed. This information may be very important in diagnosing a variety of conditions that are characterized by an abnormally low or high count.
A normal red blood cell count will vary depending on the age and sex of the person tested. The normal number for women tends to range from about 4.2-5.4 million red blood cells per microliter (million/uL). Men have a considerably higher normal range, falling between 4.7-6 million/uL. Children tend to fall somewhere in the middle of these two, and have a very narrow normal red blood cell count range of about 4.6-4.8 million/uL. Since red blood cells are essential in the movement of oxygen throughout the body, people who live at higher altitudes, where oxygen is thinner, may have a slightly higher normal range.
Having a normal number of red blood cells helps the body perform nearly every function involved with survival. The hemoglobin of RBCs is believed to transport about 98% of the body's oxygen, carrying it to and from organs like a very efficient delivery truck. When a RBC count is too low, creating a condition known as anemia, the body is at risk of not receiving sufficient oxygen, which may cause a variety of problems including organ damage. A high red blood cell count, known as polycythemia, can also be bad news; heart, lung, and blood diseases are all associated with an abnormally high RBC.
Symptoms of a lower than normal red blood cell count include fatigue, dizziness, lightheadedness, and weight loss. People with anemia may have low energy levels and be sensitive to cold. Joint pain, abdominal swelling, and excessive bruising or bleeding after minor injuries may be symptoms of polcythemia.
Checking a RBC is usually done by means of a simple blood test. It is typically performed as part of a blood panel, which checks the levels of hormones, platelets, cells, and other substances found in the bloodstream. A full blood panel may require several vials of blood to be taken, which may be cause for some concern in people with a history of anemia. Medical professionals may choose to take samples over time, or instruct an anemic patient to consume extra nutrition and get plenty of rest and fluids before coming in for testing.